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ISMERETEK ÜZEMELTETÉSI PROBLÉMÁK TERVEZÉSI HIBÁK The Boulton and Watt machines used low-pressure steam (from 5 to 15 psi), which limited both their efficiency and economy. Higher pressure (i.e., above atmospheric pressure)‏ would have permitted more powerful and economical engines, but Watt opposed it on the grounds that it increased the danger of explosion and thus constituted an unacceptable risk. The first wide-spread application of the highpressure engine, on steamboats, resulted in frequent and disastrous explosions: passengers and crew were blown up, scalded to death, hit by flying fragments of iron, and blown off steamers to drown. Accidents were also common in industrial uses of high-pressure steam. The early steam engines used inferior materials; they had low standards of workmanship; the mechanics lacked proper training and skills; and there were serious problems with quality control. The risk from this type of machine came from the boiler and not from the engine itself: It was the boiler that was exploding and causing most of the casualities. The technological development of boilers lagged behind the rapid improvement of the engines. Engineers quickly amassed scientific information about thermodynamics, the action of steam in the cylinder, the strength of materials in the engine, and many other aspects of steam engine operation. But there was little scientific understanding about the buildup of steam pressure in the boiler, the effect of corrosion and decay, and the causes of boiler explosions. Although computer hardware technology has advanced at an astounding rate, the development of software engineering has been slower. It has also been slower than required for the complex systems we want to build, like a space station or automaticallycontrolled nuclear power plants. Watt and others were correct in their belief that new standards of precision and safety were essential in the design, manufacture, and operation of the engines. These high standards were finally enforced in Britain in the latter part of the nineteenth century, and boiler explosions in Britain fell dramatically. High-Pressure Steam Engines and Computer Software Nancy G. Leveson Computer Science and Eng. Dept., FR-35 University of Washington Seattle, WA 98195 source